1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
use std::marker::PhantomData;
use crate::sys;
use crate::Ui;
/// Used to render only the visible items when displaying a
/// long list of items in a scrollable area.
///
/// For example, you can have a huge list of checkboxes.
/// Without the clipper you have to call `ui.checkbox(...)`
/// for every one, even if 99% of of them are not visible in
/// the current frame. Using the `ListClipper`, you can only
/// call `ui.checkbox(...)` for the currently visible items.
///
/// Note the efficiency of list clipper relies on the height
/// of each item being cheaply calculated. The current rust
/// bindings only works with a fixed height for all items.
pub struct ListClipper {
items_count: i32,
items_height: f32,
}
impl ListClipper {
/// Begins configuring a list clipper.
pub const fn new(items_count: i32) -> Self {
ListClipper {
items_count,
items_height: -1.0,
}
}
/// Manually set item height. If not set, the height of the first item is used for all subsequent rows.
pub const fn items_height(mut self, items_height: f32) -> Self {
self.items_height = items_height;
self
}
pub fn begin(self, ui: &Ui) -> ListClipperToken<'_> {
let list_clipper = unsafe {
let list_clipper = sys::ImGuiListClipper_ImGuiListClipper();
sys::ImGuiListClipper_Begin(list_clipper, self.items_count, self.items_height);
list_clipper
};
ListClipperToken::new(ui, list_clipper)
}
}
/// List clipper is a mechanism to efficiently implement scrolling of
/// large lists with random access.
///
/// For example you have a list of 1 million buttons, and the list
/// clipper will help you only draw the ones which are visible.
pub struct ListClipperToken<'ui> {
list_clipper: *mut sys::ImGuiListClipper,
_phantom: PhantomData<&'ui Ui>,
/// In upstream imgui < 1.87, calling step too many times will
/// cause a segfault due to null pointer. So we keep track of this
/// and panic instead.
///
/// Fixed in https://github.com/ocornut/imgui/commit/dca527b which
/// will likely be part of imgui 1.88 - at which point this can be
/// removed.
consumed_workaround: bool,
}
impl<'ui> ListClipperToken<'ui> {
fn new(_: &Ui, list_clipper: *mut sys::ImGuiListClipper) -> Self {
Self {
list_clipper,
_phantom: PhantomData,
consumed_workaround: false,
}
}
/// Progress the list clipper.
///
/// If this returns returns `true` then the you can loop between
/// between `clipper.display_start() .. clipper.display_end()`.
/// If this returns false, you must stop calling this method.
///
/// Calling step again after it returns `false` will cause imgui
/// to abort. This mirrors the C++ interface.
///
/// It is recommended to use the iterator interface!
pub fn step(&mut self) -> bool {
let is_imgui_1_88_or_higher = false;
if is_imgui_1_88_or_higher {
unsafe { sys::ImGuiListClipper_Step(self.list_clipper) }
} else {
if self.consumed_workaround {
panic!("ListClipperToken::step called after it has previously returned false");
}
let ret = unsafe { sys::ImGuiListClipper_Step(self.list_clipper) };
if !ret {
self.consumed_workaround = true;
}
ret
}
}
/// This is automatically called back the final call to
/// `step`. You can call it sooner but typically not needed.
pub fn end(&mut self) {
unsafe {
sys::ImGuiListClipper_End(self.list_clipper);
}
}
/// First item to call, updated each call to `step`
pub fn display_start(&self) -> i32 {
unsafe { (*self.list_clipper).DisplayStart }
}
/// End of items to call (exclusive), updated each call to `step`
pub fn display_end(&self) -> i32 {
unsafe { (*self.list_clipper).DisplayEnd }
}
/// Get an iterator which outputs all visible indexes. This is the
/// recommended way of using the clipper.
pub fn iter(self) -> ListClipperIterator<'ui> {
ListClipperIterator::new(self)
}
}
impl<'ui> Drop for ListClipperToken<'ui> {
fn drop(&mut self) {
unsafe {
sys::ImGuiListClipper_destroy(self.list_clipper);
};
}
}
pub struct ListClipperIterator<'ui> {
list_clipper: ListClipperToken<'ui>,
exhausted: bool,
last_value: Option<i32>,
}
impl<'ui> ListClipperIterator<'ui> {
fn new(list_clipper: ListClipperToken<'ui>) -> Self {
Self {
list_clipper,
exhausted: false,
last_value: None,
}
}
}
impl Iterator for ListClipperIterator<'_> {
type Item = i32;
fn next(&mut self) -> Option<Self::Item> {
if let Some(lv) = self.last_value {
// Currently iterating a chunk (returning all values
// between display_start and display_end)
let next_value = lv + 1;
if lv >= self.list_clipper.display_end() - 1 {
// If we reach the end of the current chunk, clear
// last_value so we call step below
self.last_value = None;
} else {
// Otherwise just increment it
self.last_value = Some(next_value);
}
}
if let Some(lv) = self.last_value {
// Next item within current step's chunk
Some(lv)
} else {
// Start iterating a new chunk
if self.exhausted {
// If the clipper is exhausted, don't call step again!
None
} else {
// Advance the clipper
let ret = self.list_clipper.step();
if !ret {
self.exhausted = true;
None
} else {
// Setup iteration for this step's chunk
let start = self.list_clipper.display_start();
let end = self.list_clipper.display_end();
if start == end {
// Somewhat special case: if a single item, we
// don't store the last_value so we call
// step() again next iteration
self.last_value = None;
} else {
self.last_value = Some(start);
}
Some(start)
}
}
}
}
}
#[test]
fn cpp_style_usage() {
// Setup
let (_guard, mut ctx) = crate::test::test_ctx_initialized();
let ui = ctx.frame();
let _window = ui
.window("Example")
.position([0.0, 0.0], crate::Condition::Always)
.size([100.0, 800.0], crate::Condition::Always)
.begin();
// Create clipper
let clip = ListClipper::new(1000);
let mut tok = clip.begin(ui);
let mut ticks = 0;
while dbg!(tok.step()) {
for row_num in dbg!(tok.display_start())..dbg!(tok.display_end()) {
dbg!(row_num);
ui.text("...");
ticks += 1;
}
}
// Check it's called an expected amount of time (only the ones
// visible in given sized window)
assert_eq!(ticks, 44);
// Calling end multiple times is fine albeit redundant
tok.end();
tok.end();
tok.end();
tok.end();
tok.end();
tok.end();
}
#[test]
fn iterator_usage() {
// Setup
let (_guard, mut ctx) = crate::test::test_ctx_initialized();
let ui = ctx.frame();
let _window = ui
.window("Example")
.position([0.0, 0.0], crate::Condition::Always)
.size([100.0, 800.0], crate::Condition::Always)
.begin();
// Create clipper
let clip = ListClipper::new(1000);
let mut ticks = 0;
let tok = clip.begin(ui);
for row_num in tok.iter() {
dbg!(row_num);
ui.text("...");
ticks += 1;
}
// Should be consistent with size in `cpp_style_usage`
assert_eq!(ticks, 44);
}